Book - Comparative Embryology of the Vertebrates 3

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Nelsen OE. Comparative embryology of the vertebrates (1953) Mcgraw-Hill Book Company, New York.

   Comparative Vertebrate Embryology 1953: 1. The Period of Preparation | 2. The Period of Fertilization | 3. The Development of Primitive Embryonic Form | 4. Histogenesis and Morphogenesis of the Organ Systems | 5. The Care of the Developing Embryo | Figures
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Part III The Development of Primitive Embryonic Form

Part III - The Development of Primitive Embryonic Form: 6. Cleavage (Segmentation) and Blastulation | 7. The Chordate Blastula and Its Significance | 8. The Late Blastula in Relation to Certain Innate Physiological Conditions: Twinning | 9. Gastrulation | 10. Tubulation and Extension of the Major Organ-forming Areas: Development of Primitive Body Form | 11. Basic Features of Vertebrate Morphogenesis

The general procedures leading to the development of primitive embryonic body form in the chordate group of animals are:

( 1 ) Cleavage. Cleavage is the division of the egg into progressively smaller cellular units, the blaslomeres (Chap. 6).

(2) Blastulation. Blastulalion results in the formation of the blastula. The blastula is composed of a cellular blastoderm in relation to a fluid-filled cavity, the blastocoel. The blastoderm of the late blastula is composed of neural, epidermal, notochordal, mesodermal, and entodermal major presumptive organ-forming areas. In the phylum Chordata, the notochordal area is the central region around which the other areas are oriented (Chap. 7). The major presumptive organ-forming areas of the late blastula exist in various degrees of differentiation (Chap. 8).

(3) Gastrulation. This is the process which effects a reorientation of the presumptive organ-forming areas and brings about their axiation antero-posteriorly in relation to the notochordal axis and the future embryonic body (Chap. 9). During gastrulation the major organ-forming areas are subdivided into minor areas or fields, each field being restricted to the development of a particular organ or part. (Pp. 378, 446, 447.

(4) Following gastrulation, the next step in the development of embryonic body form is tubulation and extension of the major organ-forming areas (Chap. 10).

(5) As tubulation and extension of the organ-forming areas is effected, the basic or fundamental conditions of the future organ systems are established, resulting in the development of primitive body form. As the development of various vertebrate embryos is strikingly similar up to this point, the primitive embryonic body forms of all vertebrates resemble each other (Chap. II).

In the drawings presented in Part III, the following scheme for designating the major organ-forming areas existing within the three germ layers is adhered to:

Cleavage (Segmentation) and Blastulation

6. Cleavage (Segmentation) and Blastulation

A. General considerations

1. Definitions

2. Early history of the cleavage (cell-division) concept

3. Importance of the cleavage-blastular period of development

a. Morphological relationships of the blastula

b. Physiological relationships of the blastula

1 ) Hybrid crosses

2) Artificial parthenogenesis

3) Oxygen-block studies

4. Geometrical relations of early cleavage

a. Meridional plane

b. Vertical plane

c. Equatorial plane

d. Latitudinal plane

5. Some fundamental factors involved in the early cleavage of the egg

a. Mechanisms associated with mitosis or cell division

b. Influence of cytoplasmic substance and egg organization upon cleavage

1) Yolk

2) Organization of the egg

c. Influence of first cleavage amphiaster on polyspermy

d. Viscosity changes during cleavage

e. Cleavage laws

1 ) Sach’s rules

2) Hertwig’s laws

6. Relation of early cleavage planes to the antero-posterior axis of the embryo

B. Types of cleavage in the phylum Chordata

1. Typical holoblastic cleavage

a. Amphioxus

b. Frog (Rana pipiens and R. sylvatica)

c. Cyclostomata

2. Atypical types of holoblastic cleavage

a. Holoblastic cleavage in the egg of the metatherian and eutherian mammals

1 ) General considerations

2) Early development of the rabbit egg

a) Two-cell stage

b) Four-cell stage

c) Eight-cell stage

d) Sixteen-cell stage

e) Morula stage

f) Early blastocyst

3) Types of mammalian blastocysts (blastulae)

b. Holoblastic cleavage of the transitional or intermediate type

1) Amhystoma maculatum (punctatum)

2) Lepidosiren paradoxa

3) Necturus maculosus

4) Acipenser sturio

5) Amia calva

6) Lepisosteus (Lepidosteus) osseus

7) Gymnophionan amphibia 3. Meroblastic cleavage

a. Egg of the common fowl

1 ) Early cleavages

2) Formation of the periblast tissue

3) Morphological characteristics of the primary blastula

4) Polyspermy and fate of the accessory sperm nuclei

b. Elasmobranch fishes

1 ) Cleavage and formation of the early blastula

2) Problem of the periblast tissue in elasmobranch fishes

c. Teleost fishes

1) Cleavage and early blastula formation

2) Origin of the periblast tissue in teleost fishes

d. Prototherian Mammalia

e. Cleavage in the California hagfish, Polistotrema (Bdellostorna) stouti

C. What is the force which causes the blastomeres to adhere together during early cleavage?

D. Progressive cytoplasmic inequality and nuclear equality of the cleavage blastomeres

1. Cytoplasmic inequality of the early blastomeres

2. Nuclear equality of the early blastomeres

E. Quantitative and qualitative cleavages and their influence upon later development

The Chordate Blastula and Its Significance

7. The Chordate Blastula and Its Significance

A. Introduction

1. Blastulae without auxiliary tissue

2. Blastulae with auxiliary or trophoblast tissue

3. Comparison of the two main blastular types

B. History of the concept of specific, organ-forming areas

C. Theory of epigenesis and the germ-layer concept of development

D. Introduction of the words ectoderm, mesoderm, endoderm

E. Importance of the blastular stage in Haeckel's theory of The Biogenetic Law of Embryonic Recapitulation

F. Importance of the blastular stage in embryonic development

G. Description of the various types of chordate blastulae with an outline of their organforming areas

1. Protochordate blastula

2. Amphibian blastula

3. Mature blastula in birds

4. Primary and secondary reptilian blastulae

5. Formation of the late mammalian blastocyst (blastula)

a. Prototherian mammal, Echidna

b. Metatherian mammal, Didelphys

c. Eutherian mammals

6. Blastulae of teleost and elasmobranch fishes

7. Blastulae of gymnophionan amphibia

Late Blastula in Relation to Certain Innate Physiological Conditions: Twinning

8. The Late Blastula in Relation to Certain Innate Physiological Conditions: Twinning

A. Introduction

B. Problem of differentiation

1. Definition of differentiation; kinds of differentiation

2. Self-differentiation and dependent differentiation

C. Concept of potency in relation to differentiation

1. Definition of potency

2. Some terms used to describe different states of potency

a. Totipotency and harmonious totipotency

b. Determination and potency limitation

c. Prospective potency and prospective fate

d. Autonomous potency c. Competence

D. The blastula in relation to twinning

1. Some definitions

a. Dizygotic or fraternal twins

b. Monozygotic or identical twins

c. Polyembryony •

2. Basis of true or identical twinning

3. Some experimentally produced, twinning conditions

E. Importance of the organization center of the late blastula


| 9. Gastrulation

A. Some definitions and concepts

1. Gastrulation

2. Primitive vertebrate body plan in relation to the process of gastrulation

a. Fundamental body plan of the vertebrate animal

b. The gastrula in relation to the primitive body plan

c. Chart of blastula, gastrula, and primitive, body-form relationships (fig. 188)

B. General processes involved in gastrulation

C. Morphogenetic movement of cells

1. Importance of cell movements during development and in gastrulation

2. Types of cell movement during gastrulation

a. Epiboly

b. Emboly

3. Description of the processes concerned with epiboly

4. Description of the processes involved in emboly

a. Involution and convergence

b. Invagination

c. Concrescence

d. Cell proliferation

e. Polyinvagination

f. Ingression

g. Delamination

h. Divergence

i. Extension

D. The organization center and its relation to the gastrulative process

1. The organization center and the primary organizer

2. Divisions of the primary organizer

E. Chemodifferentiation and the gastrulative process

F. Gastrulation in various Chordata 1. Amphioxus

a. Orientation

b. Gastrulative movements

1 ) Emboly

2) Epiboly

3) Antero-posterior extension of the gastrula and dorsal convergence of the mesodermal cells

4) Closure of the blastopore

c. Resume of cell movements and processes involved in gastrulation of Amphioxus

1 ) Emboly

2) Epiboly

2. Gastrulation in Amphibia with particular reference to the frog

a. Introduction

1) Orientation

2) Physiological changes which occur in the presumptive, organ-forming areas of the late blastula and early gastrula as gastrulation progresses

b. Gastrulation

1) Emboly

2) Epiboly

3) Embryo produced by the gastrulative processes

4) Position occupied by the pre -chordal plate material

c. Closure of the blastopore and formation of the neurenteric canal

d. Summary of morphogenetic movements of cells during gastrulation in the frog and other Amphibia

1) Emboly

2) Epiboly

3. Gastrulation in reptiles

a. Orientation

b. Gastrulation

4. Gastrulation in the chick

a. Orientation

b. Gastrulative changes

1) Development of primitive streak as viewed from the surface of stained blastoderms

2) Cell movements in the epiblast involved in primitive-streak formation as indicated by carbon-particle marking and vital-staining experiments

3) Cell movements in the hypoblast and the importance of these movements in primitive-streak formation

4) Primitive pit notochordal canal

5) Resume of morphogenetic movements of cells during gastrulation in the chick

5. Gastrulation in mammals

a. Orientation

b. Gastrulation in the pig embryo

c. Gastrulation in other mammals

6. Gastrulation in teleost and elasmobranch fishes

a. Orientation

b. Gastrulation in teleost fishes

1) Emboly

2) Epiboly

3) Summary of the gastrulative processes in teleost fishes

a) Emboly

b) Epiboly

4) Developmental potencies of the germ ring of teleost fishes

c. Gastrulation in elasmobranch fishes

7. Intermediate types of gastrulative behavior

G. The late gastrula as a mosaic of specific, organ-forming territories

H. Autonomous theory of gastrulative movements

I. Exogastrulation

J. Pre-chordal plate and cephalic projection in various chordates

K. Blastoporal and primitive-streak comparisons

Development of Primitive Body Form

10. Tubulation and Extension of the Major Organ-forming Areas: Development of Primitive Body Form

A. Introduction

1. Some of the developmental problems faced by the embryo after gastrulation

a. Tabulation

b. Increase in size and antero-posteri(*)r extension of the tubulated, major organforming areas

c. Regional modifications of the tubulated areas

2. Common, vertebrate, embryonic body form

3. Starting point for tabulation

4. Developmental processes which accomplish tabulation

a. Immediate processes

b. Auxiliary processes

5. Blastocoelic space and body-form development

6. Primitive circulatory tubes or blood vessels

7. Extra-embryonic membranes

B. Tabulation of the neural, epidermal, entodermal, and mesodermal, organ-forming areas in the vertebrate group

1. Neuralization or the tabulation of the neural plate area

a. Definition

b. Neuralizative processes in the Vertebrata

1) Thickened keel method

2) Neural fold method

c. Closure of the blastopore in rounded gastrulae, such as that of the frog

d. Anterior and posterior neuropores; neurenteric canal

2. Epidermal tabulation

a. Development of the epidermal tube in Amphibia

b. Tabulation of the epidermal area in flat blastoderms

3. Formation of the primitive gut tube (enteric tabulation)

a. Regions of primitive gut tube or early metenteron

b. Formation of the primitive metenteron in the frog

c. Formation of the tubular metenteron in flat blastoderms

4. Tabulation (coelom formation) and other features involved in the early differentiation of the mesodermal areas

a. Early changes in the mesodermal areas

1) Epimere; formation of the somites

2) Mesomere

3) Hypomere

b. Tabulation of the mesodermal areas

C. Notochordal area

D. Lateral constrictive movements

E. Tubulation of the neural, epidermal, entodermal, and mesodermal, organ-forming areas in Amphioxus

1. Comparison of the problems of tubulation in the embryo of Amphioxus with that of the embryos in the subphylum Vertebrata

a. End-bud growth

b. Position occupied by the notochord and mesoderm at the end of gastrulation

2. Neuralization and the closure of the blastopore

3. Epidermal tubulation

4. Tubulation of the entodermal area

a. Segregation of the entoderm from the chordamesoderm and the formation of the primitive metenteric tube

b. Formation of the mouth, anus, and other specialized structures of the metenteron

5. Tubulation of the mesoderm

6. Later differentiation of the myotomic (dorsal) area of the somite

7. Notochord

F. Early development of the rudiments of vertebrate paired appendages

G. The limb bud as an illustration of the field concept of development in relation to the gastrula and the tubulated embryo

H. Cephalic flexion and general body bending and rotation in vertebrate embryos

I. Influences which play a part in tubulation and organization of body form

J. Basic similarity of body-form development in the vertebrate group of chordate animals

Basic Features of Vertebrate Morphogenesis

11. Basic Features of Vertebrate Morphogenesis

A. Introduction

1. Purpose of This Chapter

2. Definitions

a. Morphogenesis and Related Terms

b. Primitive, Larval, and Definitive Body Forms (see fig. 255)

1) Primitive Body Form.

2) Larval Body Form.

3) Definitive Body Form.

3. Basic or Fundamental Tissues

B. Transformation of the Primitive Body Tubes into the Fundamental or Basic Condition of the Various Organ Systems Present in the Primitive Embryonic Body

1. Processes Involved in Basic System Formation

(a) extension and growth of the body tubes,

(b) saccular outgrowths (evaginations) and ingrowths (invaginations) from restricted areas of the tubes,

(c) cellular migrations away from the primitive tubes fo other tubes and to the spaces between the tubes, and

(d) unequal growth of different areas along the tubes.

2. Fundamental Similarity of Early Organ Systems

C. Laws of von Baer

D. Contributions of the Mesoderm to Primitive Body Formation and Later Development

1. Types of Mesodermal Cells

2. Origin of the Mesoderm of the Head Region

a. Head Mesoderm Derived from the Anterior Region of the Trunk

b. Head Mesoderm Derived from the Pre-chordal Plate

c. Head Mesoderm Contributed by Neural Crest Material

d. Head Mesoderm Originating from Post-otic Somites

3. Origin of the Mesoderm of the Tail

4. Contributions of the Trunk Mesoderm to the Developing Body

a. Early Differentiation of the Somites or Epimere

b. Early Differentiation of the Mesomere (Nephrotome)

c. Early Differentiation and Derivatives of the Hypomere

5. Embryonic Mesenchyme and Its Derivatives

1. Neural Plate Area (Ectoderm)

2. Epidermal Area (Ectoderm)

3. Entodermal Area

4. Notochordal Area

5. Mesodermal Areas

6. Germ-cell Area

F. Metamerism

G. Basic Homology of the Vertebrate Organ Systems

1. Definition

2. Basic Homology of Vertebrate Blastulae, Gastrulae, and Tubulated Embryos